Lüften - Jetzt is a free iPhone app developed by Andreas Volker in the Lifestyle category, specifically catering to weather-related concerns. The program calculates indoor humidity based on room temperature, indicating optimal times for ventilation to improve room climate. It also offers humidity forecasts for upcoming hours, aiding in the prevention of mold and dry air. By reducing the need for air conditioning, users can save energy. The app functions based on your current location or pre-selected places and provides the option for changing background images. Utilizing data from the German Weather Service, Lüften - Jetzt assures users that no personal location or data is collected.